Comparative impact of dietary carbohydrates on the liver transcriptome in two strains of mice.

Excessive long-term consumption of dietary carbohydrates, including glucose, sucrose, or fructose, has been shown to have significant impact on genome-wide gene expression, which likely results from changes in metabolic substrate flux. However, there has been no comprehensive study on the acute effects of individual sugars on the genome-wide gene expression that may reveal the genetic changes altering signaling pathways, subsequent metabolic processes, and ultimately physiological/pathological responses. Considering that gene expressions in response to acute carbohydrate ingestion might be different in nutrient sensitive and insensitive mammals, we conducted comparative studies of genome-wide gene expression by deep mRNA sequencing of the liver in nutrient sensitive C57BL/6J and nutrient insensitive BALB/cJ mice. Furthermore, to determine the temporal responses, we compared livers from mice in the fasted state and following ingestion of standard laboratory mouse chow supplemented with plain drinking water or water containing 20% glucose, sucrose, or fructose. Supplementation with these carbohydrates induced unique extents and temporal changes in gene expressions in a strain specific manner. Fructose and sucrose stimulated gene changes peaked at 3 h postprandial, whereas glucose effects peaked at 12 h and 6 h postprandial in C57BL/6J and BABL/cJ mice, respectively. Network analyses revealed that fructose changed genes were primarily involved in lipid metabolism and were more complex in C57BL/6J than in BALB/cJ mice. These data demonstrate that there are qualitative and antitative differences in the normal physiological responses of the liver between these two strains of mice and C57BL/6J is more sensitive to sugar intake than BALB/cJ.

Regulation of gene expression during the fasting-feeding cycle of the liver displays mouse strain specificity.

The liver maintains metabolic homeostasis by integrating the regulation of nutrient status with both hormonal and neural signals. Many studies on hepatic signaling in response to nutrients have been conducted in mice. However, no in-depth study is currently available that has investigated genome-wide changes in gene expression during the normal physiological fasting-feeding cycle in nutrient-sensitive and -insensitive mice. Using two strains of mice, C57BL/6J and BALB/cJ, and deploying deep RNA-Seq complemented with quantitative RT-PCR, we found that feeding causes substantial and transient changes in gene expression in the livers of both mouse strains. The majority of significantly changed transcripts fell within the areas of biological regulation and cellular and metabolic processes. Among the metabolisms of three major types of macronutrients (i.e. carbohydrates, proteins, and lipids), feeding affected lipid metabolism the most. We also noted that the C57BL/6J and BALB/cJ mice significantly differed in gene expression and in changes in gene expression in response to feeding. In both fasted and fed states, both mouse strains shared common expression patterns for about 10,200 genes, and an additional 400-600 genes were differentially regulated in one strain but not the other. Among the shared genes, more lipogenic genes were induced upon feeding in BABL/cJ than in C57BL/6J mice. In contrast, in the population of differentially enriched genes, C57BL/6J mice expressed more genes involved in lipid metabolism than BALB/cJ mice. In summary, these results reveal that the two mouse strains used here exhibit several differences in feeding-induced hepatic responses in gene expression, especially in lipogenic genes.

Mangiferin Accelerates Glycolysis and Enhances Mitochondrial Bioenergetics.

One of the main causes of hyperglycemia is inefficient or impaired glucose utilization by skeletal muscle, which can be exacerbated by chronic high caloric intake. Previously, we identified a natural compound, mangiferin (MGF) that improved glucose utilization in high fat diet (HFD)-induced insulin resistant mice. To further identify the molecular mechanisms of MGF action on glucose metabolism, we conducted targeted metabolomics and transcriptomics studies of glycolyic and mitochondrial bioenergetics pathways in skeletal muscle. These data revealed that MGF increased glycolytic metabolites that were further augmented as glycolysis proceeded from the early to the late steps. Consistent with an MGF-stimulation of glycolytic flux there was a concomitant increase in the expression of enzymes catalyzing glycolysis. MGF also increased important metabolites in the tricarboxylic acid (TCA) cycle, such as α-ketoglutarate and fumarate. Interestingly however, there was a reduction in succinate, a metabolite that also feeds into the electron transport chain to produce energy. MGF increased succinate clearance by enhancing the expression and activity of succinate dehydrogenase, leading to increased ATP production. At the transcriptional level, MGF induced mRNAs of mitochondrial genes and their transcriptional factors. Together, these data suggest that MGF upregulates mitochondrial oxidative capacity that likely drives the acceleration of glycolysis flux.

The Prostaglandin Transporter: Eicosanoid Reuptake, Control of Signaling, and Development of High-Affinity Inhibitors as Drug Candidates.

We discovered the prostaglandin transporter (PGT) and cloned the human cDNA and gene. PGT transports extracellular prostaglandins (PGs) into the cytoplasm for enzymatic inactivation. PGT knockout mice have elevated prostaglandin E2 (PGE2) and neonatal patent ductus arteriosus, which reflects PGT's control over PGE2 signaling at EP1/EP4 cell-surface receptors. Interestingly, rescued PGT knockout pups have a nearly normal phenotype, as do human PGT nulls. Given the benign phenotype of PGT genetic nulls, and because PGs are useful medicines, we have approached PGT as a drug target. Triazine library screening yielded a lead compound of inhibitory constant 50% (IC50) = 3.7 µM, which we developed into a better inhibitor of IC50 378 nM. Further structural improvements have yielded 26 rationally designed derivatives with IC50 < 100 nM. The therapeutic approach of increasing endogenous PGs by inhibiting PGT offers promise in diseases such as pulmonary hypertension and obesity.

Prostaglandin transporter modulates wound healing in diabetes by regulating prostaglandin-induced angiogenesis.

Prostaglandin transporter (PGT) mediates prostaglandin (PG) catabolism and PG signal termination. The prostanoid PGE(2), which induces angiogenesis and vasodilation, is diminished in diabetic skin, suggesting that PGT up-regulation could be important in wound healing deficiency, typified by diabetic foot ulcer. We hypothesized that up-regulation of PGT in hyperglycemia could contribute to weakened PGE(2) signaling, leading to impaired angiogenesis and wound healing. In human dermal microvascular endothelial cells (HDMECs), exposure to hyperglycemia increased PGT expression and activity up to threefold, accompanied by reduced levels of PGE(2). Hyperglycemia reduced HDMEC migration by 50% and abolished tube formation. Deficits in PGE(2) expression, HDMEC migration, and tube formation could be corrected by treatment with the PGT inhibitor T26A, consistent with the idea that PGT hyperactivity is responsible for impairments in angiogenesis mediated by PG signaling. In vivo, PGT expression was profoundly induced in diabetes and by wounding, correlating with diminished levels of proangiogenic factors PGE(2) and VEGF in cutaneous wounds of diabetic mice. Pharmacological inhibition of PGT corrected these deficits. PGT inhibition shortened cutaneous wound closure time in diabetic mice from 22 to 16 days. This effect was associated with increased proliferation, re-epithelialization, neovascularization, and blood flow. These data provide evidence that hyperglycemia enhances PGT expression and activity, leading to diminished angiogenic signaling, a possible key mechanism underlying defective wound healing in diabetes.

Nitric oxide-releasing nanoparticles accelerate wound healing by promoting fibroblast migration and collagen deposition.

Wound healing is a complex process that involves coordinated interactions between diverse immunological and biological systems. Long-term wounds remain a challenging clinical problem, affecting approximately 6 million patients per year, with a high economic impact. To exacerbate the problem, these wounds render the individual susceptible to life-threatening microbial infections. Because current therapeutic strategies have proved suboptimal, it is imperative to focus on new therapeutic approaches and the development of technologies for both short- and long-term wound management. In recent years, nitric oxide (NO) has emerged as a critical molecule in wound healing, with NO levels increasing rapidly after skin damage and gradually decreasing as the healing process progresses. In this study, we examined the effects of a novel NO-releasing nanoparticle technology on wound healing in mice. The results show that the NO nanoparticles (NO-np) significantly accelerated wound healing. NO-np modified leukocyte migration and increased tumor growth factor-ß production in the wound area, which subsequently promoted angiogenesis to enhance the healing process. By using human dermal fibroblasts, we demonstrate that NO-np increased fibroblast migration and collagen deposition in wounded tissue. Together, these data show that NO-releasing nanoparticles have the ability to modulate and accelerate wound healing in a pleiotropic manner.

Nicotinamide riboside, a trace nutrient in foods, is a vitamin B3 with effects on energy metabolism and neuroprotection.

PURPOSE OF REVIEW: This review focuses upon the biology and metabolism of a trace component in foods called nicotinamide riboside. Nicotinamide riboside is a precursor of nicotinamide adenine dinucleotide (NAD), and is a source of Vitamin B3. Evidence indicates that nicotinamide riboside has unique properties as a Vitamin B3. We review knowledge of the metabolism of this substance, as well as recent work suggesting novel health benefits that might be associated with nicotinamide riboside taken in larger quantities than is found naturally in foods. RECENT FINDINGS: Recent work investigating the effects of nicotinamide riboside in yeast and mammals established that it is metabolized by at least two types of metabolic pathways. The first of these is degradative and produces nicotinamide. The second pathway involves kinases called nicotinamide riboside kinases (Nrk1 and Nrk2, in humans). The likely involvement of the kinase pathway is implicated in the unique effects of nicotinamide riboside in raising tissue NAD concentrations in rodents and for potent effects in eliciting insulin sensitivity, mitochondrial biogenesis, and enhancement of sirtuin functions. Additional studies with nicotinamide riboside in models of Alzheimer's disease indicate bioavailability to brain and protective effects, likely by stimulation of brain NAD synthesis. SUMMARY: Initial studies have clarified the potential for a lesser-known Vitamin B3 called nicotinamide riboside that is available in selected foods, and possibly available to humans by supplements. It has properties that are insulin sensitizing, enhancing to exercise, resisting to negative effects of high-fat diet, and neuroprotecting.

Development of a high-affinity inhibitor of the prostaglandin transporter.

Prostaglandin E(2) (PGE(2)) triggers a vast array of biological signals and physiological events. The prostaglandin transporter (PGT) controls PGE(2) influx and is rate-limiting for PGE(2) metabolism and signaling termination. PGT global knockout mice die on postnatal day 1 from patent ductus arteriosus. A high-affinity PGT inhibitor would thus be a powerful tool for studying PGT function in adult animals. Moreover, such an inhibitor could be potentially developed into a therapeutic drug targeting PGT. Based on structure-activity relationship studies that built on recently identified inhibitors of PGT, we obtained N-(2-(2-(2-azidoethoxy)ethoxy)ethyl)-4-((4-((2-(2-(2-benzamidoethoxy)ethoxy)ethyl)amino)-6-((4-hydroxyphenyl)amino)-1,3,5-triazin-2-yl)amino)benzamide (T26A), a competitive inhibitor of PGT, with a K(i) of 378 nM. T26A seems to be highly selective for PGT, because it neither interacts with a PGT homolog in the organic anion transporter family nor affects PGE(2) synthesis. In Madin-Darby canine kidney cells stably transfected with PGT, T26A blocked PGE(2) metabolism, resulting in retention of PGE(2) in the extracellular compartment and the negligible appearance of PGE(2) metabolites in the intracellular compartment. Compared with vehicle, T26A injected intravenously into rats effectively doubled the amount of endogenous PGE(2) in the circulation and reduced the level of circulating endogenous PGE(2) metabolites to 50%. Intravenous T26A was also able to slow the metabolism of exogenously injected PGE(2). These results confirm that PGT directly regulates PGE(2) metabolism and demonstrate that a high-affinity inhibitor of PGT can effectively prevent PGE(2) metabolism and prolong the half-life of circulating PGE(2).

The prostaglandin transporter PGT transports PGH(2).

Prostaglandin H(2) not only serves as the common precursor of all other PGs, but also directly triggers signals (e.g. platelet aggregation), depending on its location and translocation. The prostaglandin carrier PGT mediates the transport of several prostanoids, such as PGE(2), and PGF(2alpha). Here we used PGT in the plasma membrane as a model system to test the hypothesis that PGT also transports PGH(2). Using wild-type and PGT-expressing MDCK cells, we show that PGH(2) uptake is mediated both by simple diffusion and by PGT. The PGH(2) influx permeability coefficient for diffusion is (5.66+/-0.63)x10(-6)cm/s. The kinetic parameters of PGH(2) transport by PGT are K(m)=376+/-34nM and V(max)=210.2+/-11.4 fmol/mg protein/s. PGH(2) transport by PGT can be inhibited by excess PGE(2) or by a PGT inhibitor. We conclude that PGT may play a role in transporting PGH(2) across cellular membranes.

Effect of adoptive transfer of CD4+CD25+Foxp3+ Treg induced by trichostatin A on the prevention of spontaneous abortion.

OBJECTIVE: To investigate whether epigenetic modification of CD4+CD25- T-cells in vitro can make up for the inadequacy of CD4+CD25+Foxp3+ Treg in animal model of spontaneous abortion and prevent immune response-mediated spontaneous abortion. METHODS: Trichostatin A (TSA) was applied to inhibit histone deacetylases (HDACs) and thereby to epigenetically modify the special location of Foxp3 gene in CD4+CD25- T-cells of CBA/J mice. The expressions of CD25, Foxp3, CTLA-4 and PD-1 of CD4+ T cells isolated from spleen of mice were characterized by flow cytometric analysis. Concentrations of transforming growth factor- ß (TGF-ß) and IL-10 in the supernatants of cultured Treg were measured using ELISA. The purified CD4+ T cells treated with different reagents were injected into pregnant CBA/J mice mated with DBA/2J males on Day 1 and 4 of pregnancy, respectively. The embryo resorption rate was assessed on Day 14 of pregnancy. RESULTS: TSA treatment significantly increased the population of CD4+CD25+Foxp3+ iTreg. Those TSA induced Treg expressed high levels of PD-1 and CTLA-4, and secreted high levels of TGF-ß and IL-10. Adoptive transfer of those iTreg at both early stage and implantation of stage of pregnancy significantly increased population of CD4+CD25+Foxp3+ Treg in spleens of recipient miscarriage prone mice and significantly reduced resorption in those mice. CONCLUSION: Epigenetic regulation of Foxp3 can generate functional regulatory T-cells. Adoptive transfer of TSA- induced CD4+CD25+Foxp3+ Treg at an early stage of pregnancy can induce maternal-fetal immune tolerance and reduce embryo resorption in miscarriage prone mice.

Sinus Surgery Is Associated with a Decrease in Aspirin-Induced Reaction Severity in Patients with Aspirin Exacerbated Respiratory Disease.

BACKGROUND: Nasal polyps influence the burden of aspirin-exacerbated respiratory disease (AERD) by contributing to eicosanoid production. AERD is diagnosed through graded aspirin challenges. It is not known how sinus surgery affects aspirin challenge outcomes. OBJECTIVE: To investigate the effects of endoscopic sinus surgery (ESS) on aspirin-induced reaction severity and on the levels of eicosanoids associated with these reactions. METHODS: Twenty-eight patients with AERD were challenged with aspirin before and 3 to 4 weeks after ESS. Respiratory parameters and plasma and urine levels of eicosanoids were compared before and after challenges. RESULTS: Before ESS, AERD diagnosis was confirmed in all study patients by aspirin challenges that resulted in hypersensitivity reactions. After ESS, reactions to aspirin were less severe in all patients and 12 of 28 patients (43%, P < .001) had no detectable reaction. A lack of clinical reaction to aspirin was associated with lower peripheral blood eosinophilia (0.1 K/µL [interquartile range (IQR) 0.1-0.3] vs 0.4 K/µL [IQR 0.2-0.8]; P = .006), lower urinary leukotriene E4 levels after aspirin challenge (98 pg/mg creatinine [IQR 61-239] vs 459 pg/mg creatinine [IQR 141-1344]; P = .02), and lower plasma prostaglandin D2 to prostaglandin E2 ratio (0 [±0] vs 0.43 [±0.2]; P = .03), compared with those who reacted. CONCLUSIONS: Sinus surgery results in decreased aspirin sensitivity and a decrease in several plasma and urine eicosanoid levels in patients with AERD. Diagnostic aspirin challenges should be offered to patients with suspected AERD before ESS to increase diagnostic accuracy. Patients with established AERD could undergo aspirin desensitizations after ESS as the severity of their aspirin-induced hypersensitivity reactions lessens.

Mangiferin modulation of metabolism and metabolic syndrome.

The recent emergence of a worldwide epidemic of metabolic disorders, such as obesity and diabetes, demands effective strategy to develop nutraceuticals or pharmaceuticals to halt this trend. Natural products have long been and continue to be an attractive source of nutritional and pharmacological therapeutics. One such natural product is mangiferin (MGF), the predominant constituent of extracts of the mango plant Mangifera indica L. Reports on biological and pharmacological effects of MGF increased exponentially in recent years. MGF has documented antioxidant and anti-inflammatory effects. Recent studies indicate that it modulates multiple biological processes involved in metabolism of carbohydrates and lipids. MGF has been shown to improve metabolic abnormalities and disorders in animal models and humans. This review focuses on the recently reported biological and pharmacological effects of MGF on metabolism and metabolic disorders. © 2016 BioFactors, 42(5):492-503, 2016.

Impact of high-fat diet on the proteome of mouse liver.

Chronic overnutrition, for instance, high-fat diet (HFD) feeding, is a major cause of rapidly growing incidence of metabolic syndromes. However, the mechanisms underlying HFD-induced adverse effects on human health are not clearly understood. HFD-fed C57BL6/J mouse has been a popular model employed to investigate the mechanisms. Yet, there is no systematic and comprehensive study of the impact of HFD on the protein profiles of the animal. Here, we present a proteome-wide study of the consequences of long-term HFD feeding. Utilizing a powerful technology, stable isotope labeling of mammals, we detected and quantitatively compared 965 proteins extracted from livers of chow-diet-fed and HFD-fed mice. Among which, 122 proteins were significantly modulated by HFD. Fifty-four percent of those 122 proteins are involved in metabolic processes and the majority participate in lipid metabolism. HFD up-regulates proteins that play important roles in fatty acid uptake and subsequent oxidation and are linked to the transcription factors PPARα and PGC-1α. HFD suppresses lipid biosynthesis-related proteins that play major roles in de novo lipogenesis and are linked to SREBP-1 and PPARγ. These data suggest that HFD-fed mice tend to develop enhanced fat utilization and suppressed lipid biosynthesis, understandably a self-protective mechanism to counteract to excessive fat loading, which causes liver steatosis. Enhanced fatty acid oxidation increases reactive oxygen species and inhibits glucose oxidation, which are associated with hyperglycemia and insulin resistance. This proteomics study provides molecular understanding of HFD-induced pathology and identifies potential targets for development of therapeutics for metabolic syndromes.

Medicinal properties of mangiferin, structural features, derivative synthesis, pharmacokinetics and biological activities.

The identification of biologically active and potentially therapeutically useful pharmacophores from natural products has been a long-term focus in the pharmaceutical industry. The recent emergence of a worldwide obesity and Type II diabetes epidemic has increased focus upon small molecules that can modulate energy metabolism, insulin sensitivity and fat biology. Interesting preliminary work done on mangiferin (MGF), the predominant constituent of extracts of the mango plant Mangifera indica L., portends potential for this pharmacophore as a novel parent compound for treating metabolic disorders. MGF is comprised of a C-glucosylated xanthone. Owing to the xanthone chemical structure, MGF has a redox active aromatic system and has antioxidant properties. MGF exerts varied and impressive metabolic effects in animals, improving metabolic disorders. For example we have discovered that MGF is a novel activator of the mammalian pyruvate dehydrogenase complex, leading to enhancement of carbohydrate utilization in oxidative metabolism, and leading to increased insulin sensitivity in animal models of obesity and insulin resistance. In addition, recent unbiased proteomics studies revealed that MGF upregulates proteins pivotal for mitochondrial bioenergetics and downregulates proteins controlling de novo lipogenesis in liver, helping to explain protective effects of MGF in prevention of liver steatosis. Several chemical studies have achieved synthesis of MGF, suggesting possible synthetic strategies to alter its chemical structure for development of structure-activity relationship (SAR) information. Ultimately, chemical derivatization studies could lead to the eventual development of novel therapeutics based upon the parent pharmacophore structure. Here we provide comprehensive review on chemical features of MGF, synthesis of its derivatives, its pharmacokinetics and biological activities.

Inhibition of Prostaglandin Transporter (PGT) Promotes Perfusion and Vascularization and Accelerates Wound Healing in Non-Diabetic and Diabetic Rats.

Peripheral ischemia, resulting from diminished arterial flow and defective local vascularization, is one of the main causes of impaired wound healing in diabetes. Vasodilatory prostaglandins (PGs), including PGE2 and PGI2, regulate blood flow in peripheral tissues. PGs also stimulate angiogenesis by inducing vascular endothelial growth factor. However, PG levels are reduced in diabetes mainly due to enhanced degradation. We hypothesized that inhibition of the prostaglandin transporter (PGT) (SLCO2A1), which mediates the degradation of PGs, would increase blood flow and stimulate vascularization, thereby mitigating peripheral ischemia and accelerating wound healing in diabetes. Here we report that inhibiting PGT with intravenously injected PGT inhibitor, T26A, increased blood flow in ischemic hind limbs created in non-diabetic rats and streptozotocin induced diabetic rats. Systemic, or combined with topical, T26A accelerated closure of cutaneous wounds. Immunohistochemical examination revealed that inhibition of PGT enhanced vascularization (marked by larger numbers of vessels formed by CD34+ cells), and accelerated re-epithelialization of cutaneous wounds. In cultured primary human bone marrow CD34+ cells and human epidermal keratinocytes (HEKs) either inhibiting or silencing PGT increased migration in both cell lines. Thus PGT directly regulates mobilization of endothelial progenitor cells (EPCs) and HEKs, which could contribute to PGT-mediated vascularization and re-epithelialization. At the molecular level, systemic inhibition of PGT raised circulating PGE2. Taken together, our data demonstrate that PGT modulates arterial blood flow, mobilization of EPCs and HEKs, and vascularization and epithelialization in wound healing by regulating vasodilatory and pro-angiogenic PGs.

Inhibition of the Prostaglandin Transporter PGT Lowers Blood Pressure in Hypertensive Rats and Mice.

Inhibiting the synthesis of endogenous prostaglandins with nonsteroidal anti-inflammatory drugs exacerbates arterial hypertension. We hypothesized that the converse, i.e., raising the level of endogenous prostaglandins, might have anti-hypertensive effects. To accomplish this, we focused on inhibiting the prostaglandin transporter PGT (SLCO2A1), which is the obligatory first step in the inactivation of several common PGs. We first examined the role of PGT in controlling arterial blood pressure blood pressure using anesthetized rats. The high-affinity PGT inhibitor T26A sensitized the ability of exogenous PGE2 to lower blood pressure, confirming both inhibition of PGT by T26A and the vasodepressor action of PGE2 T26A administered alone to anesthetized rats dose-dependently lowered blood pressure, and did so to a greater degree in spontaneously hypertensive rats than in Wistar-Kyoto control rats. In mice, T26A added chronically to the drinking water increased the urinary excretion and plasma concentration of PGE2 over several days, confirming that T26A is orally active in antagonizing PGT. T26A given orally to hypertensive mice normalized blood pressure. T26A increased urinary sodium excretion in mice and, when added to the medium bathing isolated mouse aortas, T26A increased the net release of PGE2 induced by arachidonic acid, inhibited serotonin-induced vasoconstriction, and potentiated vasodilation induced by exogenous PGE2. We conclude that pharmacologically inhibiting PGT-mediated prostaglandin metabolism lowers blood pressure, probably by prostaglandin-induced natriuresis and vasodilation. PGT is a novel therapeutic target for treating hypertension.

Regulation of prostaglandin EP1 and EP4 receptor signaling by carrier-mediated ligand reuptake.

After synthesis and release from cells, prostaglandin E2 (PGE2) undergoes reuptake by the prostaglandin transporter (PGT), followed by cytoplasmic oxidation. Although genetic inactivation of PGT in mice and humans results in distinctive phenotypes, and although experiments in localized environments show that manipulating PGT alters downstream cellular events, a direct mechanistic link between PGT activity and PGE2 (EP) receptor activation has not been made. Toward this end, we created two reconstituted systems to examine the effect of PGT expression on PGE2 signaling via two of its receptors (EP1 and EP4). In human embryonic kidney cells engineered to express the EP1 receptor, exogenous PGE2 induced a dose-dependent increase in cytoplasmic Ca(2+). When PGT was expressed at the plasma membrane, the PGE2 dose-response curve was right-shifted, consistent with reduction in cell surface PGE2 availability; a potent PGT inhibitor acutely reversed this shift. When bradykinin was used to induce endogenous PGE2 release, PGT expression similarly induced a reduction in Ca(2+) responses. In separate experiments using Madin-Darby Canine Kidney cells engineered to express the PGE2 receptor EP4, bradykinin again induced autocrine PGE2 signaling, as judged by an abrupt increase in intracellular cAMP. As in the EP1 experiments, expression of PGT at the plasma membrane caused a reduction in bradykinin-induced cAMP accumulation. Pharmacological concentrations of exogenous PGE2 induced EP4 receptor desensitization, an effect that was mitigated by PGT. Thus, at an autocrine/paracrine level, plasma membrane PGT regulates PGE2 signaling by decreasing ligand availability at cell surface receptors.

Dual mode action of mangiferin in mouse liver under high fat diet.

Chronic over-nutrition is a major contributor to the spread of obesity and its related metabolic disorders. Development of therapeutics has been slow compared to the speedy increase in occurrence of these metabolic disorders. We have identified a natural compound, mangiferin (MGF) (a predominant component of the plants of Anemarrhena asphodeloides and Mangifera indica), that can protect against high fat diet (HFD) induced obesity, hyperglycemia, insulin resistance and hyperlipidemia in mice. However, the molecular mechanisms whereby MGF exerts these beneficial effects are unknown. To understand MGF mechanisms of action, we performed unbiased quantitative proteomic analysis of protein profiles in liver of mice fed with HFD utilizing 15N metabolically labeled liver proteins as internal standards. We found that out of 865 quantified proteins 87 of them were significantly differentially regulated by MGF. Among those 87 proteins, 50% of them are involved in two major processes, energy metabolism and biosynthesis of metabolites. Further classification indicated that MGF increased proteins important for mitochondrial biogenesis and oxidative activity including oxoglutarate dehydrogenase E1 (Dhtkd1) and cytochrome c oxidase subunit 6B1 (Cox6b1). Conversely, MGF reduced proteins critical for lipogenesis such as fatty acid stearoyl-CoA desaturase 1 (Scd1) and acetyl-CoA carboxylase 1 (Acac1). These mass spectrometry data were confirmed and validated by western blot assays. Together, data indicate that MGF upregulates proteins pivotal for mitochondrial bioenergetics and downregulates proteins controlling de novo lipogenesis. This novel mode of dual pharmacodynamic actions enables MGF to enhance energy expenditure and inhibit lipogenesis, and thereby correct HFD induced liver steatosis and prevent adiposity. This provides a molecular basis supporting development of MGF or its metabolites into therapeutics to treat metabolic disorders.

Mangiferin stimulates carbohydrate oxidation and protects against metabolic disorders induced by high-fat diets.

Excessive dietary fat intake causes systemic metabolic toxicity, manifested in weight gain, hyperglycemia, and insulin resistance. In addition, carbohydrate utilization as a fuel is substantially inhibited. Correction or reversal of these effects during high-fat diet (HFD) intake is of exceptional interest in light of widespread occurrence of diet-associated metabolic disorders in global human populations. Here we report that mangiferin (MGF), a natural compound (the predominant constituent of Mangifera indica extract from the plant that produces mango), protected against HFD-induced weight gain, increased aerobic mitochondrial capacity and thermogenesis, and improved glucose and insulin profiles. To obtain mechanistic insight into the basis for these effects, we determined that mice exposed to an HFD combined with MGF exhibited a substantial shift in respiratory quotient from fatty acid toward carbohydrate utilization. MGF treatment significantly increased glucose oxidation in muscle of HFD-fed mice without changing fatty acid oxidation. These results indicate that MGF redirects fuel utilization toward carbohydrates. In cultured C2C12 myotubes, MGF increased glucose and pyruvate oxidation and ATP production without affecting fatty acid oxidation, confirming in vivo and ex vivo effects. Furthermore, MGF inhibited anaerobic metabolism of pyruvate to lactate but enhanced pyruvate oxidation. A key target of MGF appears to be pyruvate dehydrogenase, determined to be activated by MGF in a variety of assays. These findings underscore the therapeutic potential of activation of carbohydrate utilization in correction of metabolic syndrome and highlight the potential of MGF to serve as a model compound that can elicit fuel-switching effects.

Aging-shifted prostaglandin profile in endothelium as a factor in cardiovascular disorders.

Age-associated endothelium dysfunction is a major risk factor for the development of cardiovascular diseases. Endothelium-synthesized prostaglandins and thromboxane are local hormones, which mediate vasodilation and vasoconstriction and critically maintain vascular homeostasis. Accumulating evidence indicates that the age-related changes in endothelial eicosanoids contribute to decline in endothelium function and are associated with pathological dysfunction. In this review we summarize currently available information on aging-shifted prostaglandin profiles in endothelium and how these shifts are associated with cardiovascular disorders, providing one molecular mechanism of age-associated endothelium dysfunction and cardiovascular diseases.